May 18 (GMM) One Honda engineer has broken ranks and admitted the Japanese marque will not power a McLaren driver to victory in 2015.

Despite the difficult, uncompetitive and unreliable birth in 2015 to the new works McLaren-Honda alliance, the 'graphite-grey' outfit has been a near-perfect picture of optimism.

Drivers and bosses are refusing even to rule out race wins, with Honda's F1 chief Yasuhisa Arai saying last week that catching up to Mercedes by season end remains the target.

But when asked if Fernando Alonso and Jenson Button will be in a position to win races in 2015, Honda engineer Ryo Mukumoto admitted categorically: "No.

"And next year it will also be difficult," he is quoted by the Spanish sports daily Marca.

"For a new team it is difficult to win the first race when the others have been working much longer. In 2016 we will try to win a race, but there are no guarantees in the world of motor sport," said the Japanese.

Mukumoto's goal for McLaren-Honda in 2015, therefore, is more modest.

"Our goal is to approach the third team at the end of this season. If we succeed, it will be a great achievement," he said.

He revealed that Honda still has much to extract from its troublesome 2015 'power unit'.

"We are not close to the limit," said Mukomoto. "We are still improving, but it is not simple. We fight, but we are still far away.

"We cannot take it to the limit as other teams can. Our engineers have managed to extract 70 per cent of the power so far."

This season, therefore, is as much about learning for the future than achieving actual results, he suggested.

"We have to gather experience," said Mukomoto, "because our engine is new. We cannot make comparisons with the other manufacturers.

"Before using this design we did several investigations," he added. "I must admit that some did not work, but when we use our tokens it will be much better."